There are many golf club heads in which the head body forms a hollow structure. In recent years, the wall thickness of the head body of this type of golf club head has been progressively reduced for the purpose of reducing the weight of the golf club head. However, this reduction in wall thickness reduces the rigidity of the golf club head, and a reduction in rigidity tends to lead to the problem of a low and dull ball hitting sound that is generally unfavorable.
In view of this, there are cases where a rib is formed on an inner surface of the head body in order to solve the above problem (see Patent Literatures JP H10-24128A, JP 2002-186691A and JP 2009-233266A). This rib effectively improves the rigidity of the golf club head, which had been reduced by the reduction in the wall thickness of the head body, thus making it possible to increase the natural frequency of the golf club head. As a result, a reduction in wall thickness is achieved, and a high and pleasant-sounding ball hitting sound is also obtained.